There are many natural gas liquefaction methods.
In particular, U.S. Pat. No. 6,105,389 describes a liquefaction method using two coolant circuits. Although it is effective, this method requires a large amount of energy, and therefore implementation of very expensive gas turbines.
U.S. Pat. No. 6,449,982 describes a liquefaction method allowing to liquefy only part of the gas treated. The power required for liquefaction is therefore reduced. However, a drawback of this method lies in the use of the excess gas, insofar as the liquefaction site is often far from the places of use.
U.S. Pat. No. 6,248,794 describes various integrations of a Fischer-Tropsch process with a natural gas liquefaction method. In particular, it proposes using the residual gas from the Fischer-Tropsch process in the gas turbines operating the refrigeration compressors, or using steam turbines to operate the refrigeration compressors, the steam being produced in the Fischer-Tropsch unit.
The present invention provides a method allowing to best upgrade all of the natural gas from an oil well by proposing integration of a low-temperature liquefaction method and of a Fischer-Tropsch process.